Buy BOOKS at Discounted Price

Natural Resources

Class 9th Science NCERT Exemplar Solution
Multiple Choice Questions
  1. The atmosphere of the earth is heated by radiations which are mainlyA. radiated by the sun…
  2. If there were no atmosphere around the earth, the temperature of the earth willA. increase…
  3. What would happen, if all the oxygen present in the environment is converted to ozone?A.…
  4. One of the following factors does not lead to soil formation in natureA. the sun B. water…
  5. The two forms of oxygen found in the atmosphere areA. water and ozone B. water and oxygen…
  6. The process of nitrogen-fixation by bacteria does not take place in the presence ofA.…
  7. Rainfall patterns depend onA. the underground water table B. the number of water bodies in…
  8. Among the given options, which one is not correct for the use of large amount of…
  9. The nitrogen molecules present in air can be converted into nitrates and nitrites byA. a…
  10. One of the following processes is not a step involved in the water-cycle operating in…
  11. The term water-pollution can be defined in several ways. Which of the following statements…
  12. Which of the following is not a greenhouse gas?A. Methane B. Carbon dioxide C. Carbon…
  13. Which step is not involved in the carbon-cycle?A. Photosynthesis B. Transpiration C.…
  14. Ozone-hole meansA. a large sized hole in the ozone layer B. thinning of the ozone layer C.…
  15. Ozone-layer is getting depleted because ofA. excessive use of automobiles B. excessive…
  16. Which of the following is a recently originated problem of environment?A. Ozone layer…
  17. When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of…
  18. Top-soil contains the followingA. Humus and living organisms only B. Humus and soil…
  19. Choose the correct sequencesA. CO2 in atmosphere decomposers organic carbon in animals…
  20. Major source of mineral in soil is theA. parent rock from which soil is formed B. plants…
  21. Total earths surface covered by water isA. 75% B. 60% C. 85% D. 50%…
  22. Biotic component of biosphere is not constituted byA. producers B. consumers C. decomposer…
  23. An increase in carbon dioxide content in the atmosphere would not causeA. more heat to be…
  24. Oxygen is returned to the atmosphere mainly byA. burning of fossil fuel B. respiration C.…
  25. Low visibility during cold weather is due toA. formation of fossil fuel B. unburnt carbon…
  26. Growth of Lichens on barren rocks is followed by the growth ofA. moss B. ferns C.…
  27. Marked temperature changes in aquatic environment can affectA. breeding of animals B. more…
  28. Soil erosion can be prevented byA. raising forests B. deforestation C. excessive use of…
  29. What happens when rain falls on soil without vegetational cover?A. Rainwater percolates in…
  30. Oxygen is harmful forA. ferns B. nitrogen fixing bacteria C. chara D. mango tree…
Short Answer Type
  1. Rivers from land, add minerals to sea water. Discuss how?
  2. How can we prevent the loss of top layer of soil?
  3. How is the life of organisms living in water affected when water gets polluted?…
  4. During summer, if you go near the lake, you feel relief from the heat, why?…
  5. In coastal area, wind current moves from the sea towards the land during day; but during…
  6. Following are a few organisms (a) lichen (b) mosses (c) mango tree (d) cactus Which among…
  7. Soil formation is done by both abiotic and biotic factors. List the names of these factors…
  8. All the living organisms are basically made up of C, N, S, P, H and O. How do they enter…
  9. Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost…
  10. Why does moon have very cold and very hot temperature variations eg, from -190C to 110C…
  11. Why do people love to fly kites near the seashore ?
  12. Why does Mathura refinery pose problems to the Taj Mahal?
  13. Why do not lichens occur in Delhi whereas they commonly grow in Manali or Darjeeling?…
  14. Why does water need conservation even though large oceans surround the land masses?…
  15. There is mass mortality of fishes in a pond. What may be the reasons?…
  16. Lichens are called pioneer colonisers of bare rock. How can they help in formation of…
  17. Soil is formed by water. If you agree to this statement then give reasons…
  18. Fertile soil has lots of humus. Why?
  19. Why step farming is common in hills?
  20. Why are root nodules useful for the plants?
Long Answer Type
  1. How do fossil fuels cause air pollution?
  2. What are the causes of water pollution? Discuss how you can contribute in reducing water…
  3. A motor car, with its glass totally closed, is parked directly under the sun.…
  4. Justify Dust is a pollutant ?
  5. Explain the role of the Sun in the formation of soil.
  6. Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?…

Multiple Choice Questions
Question 1.

The atmosphere of the earth is heated by radiations which are mainly
A. radiated by the sun

B. re-radiated by land

C. re-radiated by water

D. re-radiated by land and water


Answer:

The Earth's energy comes from the Sun and the energy is lost when the earth re-radiates it into the outer space. The earth system is made up of water, ice, atmosphere, etc. The atmosphere of the earth is heated by radiations which are mainly re-radiated by land and water.


Question 2.

If there were no atmosphere around the earth, the temperature of the earth will
A. increase

B. go on decreasing

C. increase during day and decrease during night

D. be unaffected


Answer:

Our earth will become like mercury. If it does not have atmosphere so first of all there will be no seasons. Hence, Surface Temp. of earth will erose too high at direct exposure of sun and will be too cold when there will be no sun.


Question 3.

What would happen, if all the oxygen present in the environment is converted to ozone?
A. We will be protected more

B. It will become poisonous and kill living forms

C. Ozone is not stable, hence it will be toxic

D. It will help harmful sun radiations to reach earth and damage many life forms.


Answer:

Ozone will damage living tissues and the man-made things. The temperature will rise and metals will melt. Water will start to evaporate and eventually living beings will die.


Question 4.

One of the following factors does not lead to soil formation in nature
A. the sun

B. water

C. wind

D. polythene bags


Answer:

Polythene bags can best be defined as a non-biodegradable substance that penetrates into the soil which in turn affects food growth and development. It blocks the synthesis of any natural material or process that comes in its way. Thus, it also hampers the soil formation in nature.


Question 5.

The two forms of oxygen found in the atmosphere are
A. water and ozone

B. water and oxygen

C. ozone and oxygen

D. water and carbon-dioxide


Answer:

Elemental oxygen is normally found in the form of a diatomic molecule In the upper layers of atmosphere another form of oxygen that is a triatomic molecule of oxygen and it is called ozone (O3). Thus, the two forms of oxygen found in the atmosphere are O2 Oxygen and (O3) (ozone).


Question 6.

The process of nitrogen-fixation by bacteria does not take place in the presence of
A. molecular form of hydrogen

B. elemental form of oxygen

C. water

D. elemental form of nitrogen


Answer:

Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called a nitrogenase. The reaction for BNF is as follows


N2+ 8 H+ + 8 e→ 2 NH3 + H. The process is coupled to the hydrolysis of 16 equivalents of ATP and is accompanied by the co-formation of one molecule of H2


Question 7.

Rainfall patterns depend on
A. the underground water table

B. the number of water bodies in an area

C. the density pattern of human population in an area

D. the prevailing season in an area


Answer:

Rainfall and its total mount, frequency and intensity, these values vary from place to place, day to day, month to month and also year to year. It depends upon the season and type of climatic conditions including demography of that area.


Question 8.

Among the given options, which one is not correct for the use of large amount of fertilisers and pesticides?
A. They are eco-friendly

B. They turn the fields barren after some time

C. They adversely affect the useful component from the soil

D. They destroy the soil fertility


Answer:

Fertilizers and pesticides washes into waterways along with eroded sediments. This nitrogen fertilizer easily dissolved into waters and causes eutrophication* and "dead zones" that kill aquatic life. It is not eco-friendly.


*Eutrophication: Eutrophication is due to excessive nutrient supply in the water bodies which


Question 9.

The nitrogen molecules present in air can be converted into nitrates and nitrites by
A. a biological process of nitrogen fixing bacteria present in soil

B. a biological process of carbon fixing factor present in soil

C. any of the industries manufacturing nitrogenous compounds

D. the plants used as cereal crops in field


Answer:

Nitrogen fixation is a process by which nitrogen in the Earth's atmosphere is converted into ammonia (NH3) or other molecules available to living organisms. Atmospheric nitrogen or molecular dinitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds.


Question 10.

One of the following processes is not a step involved in the water-cycle operating in nature
A. evaporation

B. transpiration

C. precipitation

D. photosynthesis


Answer:

The water cycle consists of three major processes: evaporation, condensation, and precipitation. Evaporation is the process of a liquid's surface changing to a gas. In the water cycle, liquid water (in the ocean, lakes, or rivers) evaporates and becomes water vapor. It condenses in the atmosphere and comes back as precipitation (rain) back to earth.


Question 11.

The term “water-pollution” can be defined in several ways. Which of the following statements does not give the correct definition?
A. The addition of undesirable substances to water-bodies

B. The removal of desirable substances from water-bodies

C. A change in pressure of the water bodies

D. A change in temperature of the water bodies


Answer:

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater). This form of environmental degradation occurs when pollutants are directly or indirectly discharged into water bodies without adequate treatment to remove harmful compounds.


Question 12.

Which of the following is not a greenhouse gas?
A. Methane

B. Carbon dioxide

C. Carbon monoxide

D. Ammonia


Answer:

Ammonia contains no carbon and releases no greenhouse gases. The emission of direct and indirect greenhouse gases, namely methane (CH4), carbon dioxide (CO2), ammonia (NH3), nitric (NO) and nitrous oxide (N2O)


Question 13.

Which step is not involved in the carbon-cycle?
A. Photosynthesis

B. Transpiration

C. Respiration

D. Burning of fossil fuels


Answer:

Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. It is kind of evaporation of water from plant leaves.


Question 14.

‘Ozone-hole’ means
A. a large sized hole in the ozone layer

B. thinning of the ozone layer

C. small holes scattered in the ozone layer

D. thickening of ozone in the ozone layer


Answer:

severe depletion of ozone in a region of the ozone layer and it is caused by the destruction of ozone by CFCs and by other compounds, such as carbon tetrachloride (CCl4) and carbon tetrafluoride (CF4).


Question 15.

Ozone-layer is getting depleted because of
A. excessive use of automobiles

B. excessive formation of industrial units

C. excessive use of man-made compounds containing both fluorine and chlorine

D. excessive deforestation.


Answer:

Ozone depletion occurs when chlorofluorocarbons (CFCs)—formerly found in aerosol spray cans and refrigerants—are released into the atmosphere. These gases, through several chemical reactions, cause the ozone molecules to break down, reducing ozone ultraviolet (UV) radiation-absorbing capacity.


Question 16.

Which of the following is a recently originated problem of environment?
A. Ozone layer depletion

B. Greenhouse effect

C. Global warming

D. All of the above


Answer:

All the problems have deteriorated the environment. Greenhouse leads to global warming and ozone layer depletion has led to many diseases in human beings.


Question 17.

When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of this nitrogen?
A. It moves along with oxygen into the cells

B. It comes out with the CO during exhalation

C. It is absorbed only by the nasal cells

D. Nitrogen concentration is already more in the cells so it is not at all absorbed.


Answer:

Nitrogen being unreactive is not used in respiration at all. we simply breathe the nitrogen back out again, unchanged along with CO.


Question 18.

Top-soil contains the following
A. Humus and living organisms only

B. Humus and soil particles only

C. Humus, living organisms and plants

D. Humus, living organisms and soil particles.


Answer:

Topsoil is the upper, outermost layer of soil, usually the top 2 inches (5.1 cm) to 8 inches (20 cm). It has the highest concentration of organic matter and microorganisms and it is the place where most of the Earth's biological soil activity occurs.


Question 19.

Choose the correct sequences
A. CO2 in atmosphere → decomposers → organic carbon in animals → organic carbon in plants

B. CO in atmosphere → organic carbon in plants → organic carbon in animals → inorganic carbon in soil

C. Inorganic carbonates in water → organic carbon in plants → organic carbon in animals → scavengers

D. Organic carbon in animals → decomposers → CO in atmosphere → organic carbon in plants


Answer:

Carbon dioxide is taken up by Plants during Photosynthesis and it is fixed into organic carbon source which is taken up by animals which feed on plants and so on. At the end, the decomposers break down the dead remains of plants and animals and this releases the carbon in an inorganic form into the soil.


Question 20.

Major source of mineral in soil is the
A. parent rock from which soil is formed

B. plants

C. animals

D. bacteria


Answer:

Soil is a mixture of minerals, organic matter, gases, liquids, and countless organisms that live inside and on it. Rock, is the source of all soil mineral materials and the origin of all plant nutrients


Question 21.

Total earth’s surface covered by water is
A. 75%

B. 60%

C. 85%

D. 50%


Answer:

About 75% percent of the Earth's surface is water-covered, and the oceans hold about 96.5 percent of all Earth's water. Water also exists in the air as water vapor, in rivers and lakes, in icecaps and glaciers, in the ground as soil moisture and in aquifers, and even in humans and animals.


Question 22.

Biotic component of biosphere is not constituted by
A. producers

B. consumers

C. decomposer

D. air


Answer:

Biotic components are the living things that shape an ecosystem. Air is an abiotic component.


Question 23.

An increase in carbon dioxide content in the atmosphere would not cause
A. more heat to be retained by the environment

B. increase in photosynthesis in plants

C. global warming

D. abundance of desert plants


Answer:

If CO2 level will increase temperatures throughout the Earth. However, soil conditions will not necessarily favor growth of dry land plants.


Question 24.

Oxygen is returned to the atmosphere mainly by
A. burning of fossil fuel

B. respiration

C. photosynthesis

D. fungi


Answer:

The oxygen cycle is the biogeochemical cycle. The main source of atmospheric free oxygen is photosynthesis, which produces sugars and free oxygen from carbon dioxide and water and gives it to atmosphere.


Question 25.

Low visibility during cold weather is due to
A. formation of fossil fuel

B. unburnt carbon particles or hydrocarbons suspended in air

C. lack of adequate power supply

D. none of these


Answer:

In the winter months when the wind speeds are low, smoke and fog become stagnate at a place forming smog and increasing pollution levels near the ground closer to where people are respiring. It hampers visibility and disturbs the environment.


Question 26.

Growth of Lichens on barren rocks is followed by the growth of
A. moss

B. ferns

C. gymnosperms

D. algae


Answer:

Moss (division Bryophyta), any of at least 12,000 species of small non vascular spore-bearing land plants. They are small flowerless plants that typically grow in dense green clumps or mats, often in damp or shady locations. The individual plants are usually composed of simple leaves that are generally only one cell thick, attached to a stem that may be branched or unbranched and has only a limited role in conducting water and nutrients.


Question 27.

Marked temperature changes in aquatic environment can affect
A. breeding of animals

B. more growth of aquatic plants

C. process of digestion in animals

D. availability of nutrients.


Answer:

Rising temperatures can directly affect the metabolism, life cycle, and behaviour of aquatic animals.


Question 28.

Soil erosion can be prevented by
A. raising forests

B. deforestation

C. excessive use of fertilizer

D. overgrazing by animals


Answer:

Trees reduce the rate of erosion by protecting the soil from the impact of rain. transpiring large amounts of water, which counteracts very wet soil and binding soil to sloping land with their roots.


Question 29.

What happens when rain falls on soil without vegetational cover?
A. Rainwater percolates in soil efficiently

B. Rainwater causes loss of surface soil

C. Rainwater leads to fertility of the soil

D. Rainwater does not cause any change in soil


Answer:

Soil erosion is a naturally occurring process that affects all landforms. Rainfall may also move soil indirectly, by means of runoff in rills (small channels) or gullies (larger channels, too big to be removed by tillage). In many parts of the world, rill and gully erosion is the dominant form of water erosion.


Question 30.

Oxygen is harmful for
A. ferns

B. nitrogen fixing bacteria

C. chara

D. mango tree


Answer:

The symbiotic nitrogen-fixing bacteria invade the root hairs of host plants, where they multiply and stimulate formation of root nodules, enlargements of plant cells and bacteria in intimate association. Within the nodules the bacteria convert free nitrogen to ammonia, which the host plant utilizes for its development. To ensure sufficient nodule formation and optimum growth of legumes (e.g., alfalfa, beans, clovers, peas, soybeans). However the nitrogen-fixing enzyme, nitrogenase, is unstable in the presence of oxygen.



Short Answer Type
Question 1.

Rivers from land, add minerals to sea water. Discuss how?


Answer:

Water is capable of dissolving a large number of substances. As water flows over the rocks containing soluble minerals, some of them get dissolved in the water. Thus, rivers carry many nutrients from land to the sea.



Question 2.

How can we prevent the loss of top layer of soil?


Answer:

Loss of topsoil can be prevented by

(i) increasing the vegetational cover


(ii) checking the falling of trees


(iii) by preventing excessive grazing by animals


Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time by animals. The animals should be limited to particular space and should also be monitored when grazing. They should also be given alternate source of feed for their survival.



Question 3.

How is the life of organisms living in water affected when water gets polluted?


Answer:

Addition of undesirable chemicals like pesticides, fertilizers, industrial waste and domestic wastes not only kill the organisms, they also cause diseases to the aquatic organisms. Besides, the requirement of oxygen by aquatic organisms is also increased. There is a reduction in the dissolved oxygen in water which adversely affects the aquatic organisms.



Question 4.

During summer, if you go near the lake, you feel relief from the heat, why?


Answer:

Air near water bodies is cooled due to evaporation of water. Heat raises the air and creates a vacuum below. Evaporation cooles down the water and surrounding and thus area near lake is cooler as compared to other areas and we feel relief from heat.



Question 5.

In coastal area, wind current moves from the sea towards the land during day; but during night it moves from land to the sea. Discuss the reason.


Answer:

Air above the land gets heated quickly during day and starts rising. This creates a region of low pressure as a result air over sea rushes into this area of low pressure. This movement of air from one region to the other creates winds. During night, as water cools down slowly, the air above water is warmer than the air on land. So air moves from land to sea creating winds.



Question 6.

Following are a few organisms

(a) lichen (b) mosses

(c) mango tree (d) cactus

Which among the above can grow on stones; and also help in formation of soil? Write the mode of their action for making soil.


Answer:

Lichens and Mosses (a) and (b). Lichens and mosses release substances which break down the stones resulting in the formation of soil.

The fungal component of lichens produces organic acids that disintegrate rock, giving the lichen a better hold and contributing to the weathering process, which eventually turns a rock into soil.


As lichens die, they provide some organic matter that also contributes to soil. Mosses can then colonize the thin soil; as mosses die, the soil thickens more allowing other hardy species to colonize.



Question 7.

Soil formation is done by both abiotic and biotic factors. List the names of these factors by classifying them as abiotic and biotic?


Answer:

Abiotic factors making soil are sun, water and wind

Biotic factors making soil are lichens, mosses and trees.



Question 8.

All the living organisms are basically made up of C, N, S, P, H and O. How do they enter the living forms? Discuss.


Answer:

Through photosynthesis and absorption from soil. A nutrient cycle (or ecological recycling) is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems. Ecosystems are interconnected systems where matter and energy flows and is exchanged as organisms feed, digest, and migrate from one place to another.



Question 9.

Why does the percentage of gases like oxygen, nitrogen and carbon dioxide remain almost the same in the atmosphere?


Answer:

Cycling of these gases maintains consistency and biotic and abiotic factors contribute in the maintenance of balance.



Question 10.

Why does moon have very cold and very hot temperature variations eg, from -190°C to 110°C even though it is at the same distance from the sun as the earth is?


Answer:

It is due to the fact there is no atmosphere on the moon. Our moon does indeed have an atmosphere consisting of some unusual gases, including sodium and potassium, which are not found in the atmospheres of Earth, Mars or Venus.



Question 11.

Why do people love to fly kites near the seashore ?


Answer:

people love to fly kites near the seashore because during day the air above land gets heated faster and starts rising. So the air above the sea moves into this area rapidly.



Question 12.

Why does Mathura refinery pose problems to the Taj Mahal?


Answer:

Mathura refinery releases toxic gases (like oxides of sulphur) which causes acid rain and hence corrosion of the marbles of Taj Mahal.

The Mathura Refinery, is located in Mathura, Uttar Pradesh. The refinery processes low sulphur crude from Bombay High, imported low sulphur crude from Nigeria, and high sulphur crude from the Middle East. The Mathura oil refinery releases toxic gases and disposes waste into the rivers making the area dirty and unhealthy. the air has high levels of suspended particulate matter, caused by factory emissions, dust, construction, and exhaust from automobiles. These are causing the Taj Mahal to change color



Question 13.

Why do not lichens occur in Delhi whereas they commonly grow in Manali or Darjeeling?


Answer:

It is a bio-indicator and sensitive to pollution from automobiles. Lichens are highly susceptible towards sulphur dioxide. A compound in them reacts with sulphur dioxide to form a poisonous chemical that kills the plant itself. Delhi has maximum number of automobiles, hence has a highly polluted environment and lichens do not grow here.



Question 14.

Why does water need conservation even though large oceans surround the land masses?


Answer:

Marine water is not useful for human and plant life directly. Uneven distribution of limited freshwater resources need conservation to cater to the demands.



Question 15.

There is mass mortality of fishes in a pond. What may be the reasons?


Answer:

The following can be the reasons for the mass mortality of fishes in the pond.

(i)Thermal pollution


(ii) Addition of poisonous (mercury) compounds in water


(iii) Due to blockage of gills with any pollutant.


(iv) Domestic Sewage


(v) Eutophication


(vi) Thermal Waste Water Discharge



Question 16.

Lichens are called pioneer colonisers of bare rock. How can they help in formation of soil?


Answer:

Lichens release chemical substances to break the rocks into smaller particles and hence make soil. They enrich the soil by trapping water, dust and silt. When lichens die they contribute organic matter to the soil, improving the soil so that other plants can grow there.



Question 17.

“Soil is formed by water.” If you agree to this statement then give reasons


Answer:

Water helps in formation of soil in following ways.

(i) Water causes ‘wear off’ of rocks over a long period of time.


(ii) It also causes the rocks to rub against other rocks creating small particles which are taken away downstream and deposited as soil.


(iii) Water expands on freezing in crevices of rocks and cracks rocks into smaller pieces.



Question 18.

Fertile soil has lots of humus. Why?


Answer:

Fertile soils are rich in organisms that decomposes dead organic matter forming humus. Humus gives minerals, absorbs water and makes soil porous. It is also able to absorb more air and water.



Question 19.

Why step farming is common in hills?


Answer:

Step farming is practiced to check soil erosion through water currents on the slopes. It is more commonly known as terracing farming. In agriculture, a terrace is a leveled section of a hilly cultivated area, designed as a method of soil conservation to slow or prevent the rapid surface runoff of irrigation water. Often such land is formed into multiple terraces, giving a stepped appearance. This type of farming in land use is prevalent in many countries, and is used for crops requiring a lot of water, such as rice. Terraces are also easier for both mechanical and manual sowing and harvesting than a steep slope.



Question 20.

Why are root nodules useful for the plants?


Answer:

In root nodules nitrogen fixing Rhizobium bacteria are present which increases the soil fertility.Bacteria living in the root nodules fix atmospheric nitrogen to the plant.

Plants cannot utilize atmospheric nitrogen directly. Hence, leguminous plants establish a symbiotic relationship with bacteria like Rhizobium. Leguminous plant provides shelter and nourishment for the bacteria and in turn bacteria fix atmospheric nitrogen to the plant.




Long Answer Type
Question 1.

How do fossil fuels cause air pollution?


Answer:

The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When fossil fuels are burnt, it produces oxides of nitrogen and sulphur. These gases cause inhalation problems and in presence of rain forms acid rain. Burning of fossil fuels also increase the amount of suspended particles in air that reduce the visibility.



Question 2.

What are the causes of water pollution? Discuss how you can contribute in reducing water pollution.


Answer:

(i) undesirable substances like fertilizers and pesticides or any poisonous substances.

(ii) sewage directly entering a water body.


(iii) hot water from the power plant that increases the temperature and reduces the dissolved oxygen in water thus killing the aquatic organisms.


(iv) industrial effluents or radioactive substances in water body.


We can take following measures to check water pollution


(i) The sewer lines should not be directly connected to the water body.


(ii) We should not throw our garbages or domestic waste in the water body.


(iii) Prevent dumping of toxic compounds in the water bodies.


(iv) Washing of clothes should be avoided near water bodies as it adds lot of detergents to it.


(v) Plant trees near the banks of the river to check soil erosion otherwise erosion leads to siltation of water body.



Question 3.

A motor car, with its glass totally closed, is parked directly under the sun.


Answer:

The inside temperature of the car rises very high. Explain why?

Infra-red radiations in sunlight pass through the glass and heat the interior of the car. The radiation emitted by upholstery and other inner parts of the car cannot pass out of the glass, so the heat trapped inside raises the temperature of the interior. This is because glass is transparent to infrared radiation from the sun having smaller wavelength than that emitted by the interior of the car which are of longer wavelength to which the glass is opaque.



Question 4.

Justify “Dust is a pollutant” ?


Answer:

Dust remains present in air as suspended particles can cause allergy and other respiratory diseases. It also affects plant growth, by covering stomata on leaf surface. It acts as the carrier of toxic compounds like heavy metals.



Question 5.

Explain the role of the Sun in the formation of soil.


Answer:

The rocks are heated by the sun; they contract during night but not at same rate during the day. It results in cracks in rocks and ultimately to smaller particles. These small particles further break down into soil.



Question 6.

Carbon dioxide is necessary for plants. Why do we consider it as a pollutant?


Answer:

Increasing concentration (more than normal) of CO is harmful and considered as a pollutant. Higher concentrations of CO2 leads to greenhouse effect/global warming. Increased level of CO leads to pollution.